We consider the problem of cross-band interference when devices from the same or different networks share radio spectrum. Cross-band interference occurs when unsynchronized transmissions create harmful interference among each other although they use non-overlapping frequency bands. We perform an in-depth study to analytically quantify the degree of interference and its impact on OFDMA-based packet transmissions. The analysis also takes into account practical artifacts including temporal sampling mismatch, frequency offset and power heterogeneity. Using insights from the analysis, we build and compare three methods that apply temporal and frequency redundancy to reduce the interference and add robustness against it. Experimental and analytical results show that adding frequency guardband is the most efficient solution to tackle cross-band interference. Categories and Subject Descriptors C.2.1 [Network Architecture and Design]: Wireless communication General Terms Algorithms, Design, ...